Roller bearing with cage fastener

ABSTRACT

A roller bearing with cage fasteners that prevent cage separation under adverse operating conditions. The roller bearing has an inner race, outer race, a plurality of rollers, a roller cage, and cage fasteners. The inner race is disposed about a rotational axis and includes a peripheral surface facing the rotational axis with an inner nominal diameter of seven inches about the rotational axis. The outer race has a circumferential surface surrounding the inner race and includes an outer nominal diameter of twelve inches about the rotational axis. The roller cage is disposed between the inner race and the outer race and includes a first piece and a second piece connected together by the cage fasteners. Each of the cage fasteners includes a first surface having a first effective area in contiguous engagement with the first piece of the roller cage, and a second surface having a second effective area in contiguous engagement with the second piece of the roller cage. The first and second effective areas are generally equal to each other.

PRIORITY

This application claims the benefits under 35 U.S.C. § 119 of copendingU.S. Provisional Application Ser. No. 60/384,181 filed on 30 May 2002(Attorney Docket No. 039613-0000), entitled “Cylindrical Roller Bearingwith Cage Fastener,” which Provisional Application is herebyincorporated by reference in its entirety in this application.

BACKGROUND OF THE INVENTION

A roller bearing can utilize a cage with multiple parts that arefastened with swaged fasteners to retain the rollers in the cage. In thelocomotive industry, a known roller bearing utilizing swaged fastenersfor a cage has a “pitch” diameter of about 10 inches. The “pitch”diameter of the bearing is generally two times a distance between thecenterline of the rollers with respect to a rotational axis of thebearing. The known roller bearing has a two-piece cage to retain aplurality of rollers between outer and inner races. The cage has anannular cover and an annular base with projecting fingers arranged in anequiangular array about the rotational axis. Each swaged fastener cansecure the annular cover to the annular base of the cage by initiallymounting a shank portion of the fastener through apertures formedthrough the cover and base of the cage. A force, i.e., a preload, toensure that the cage cover and base are fixed to each other is appliedthrough the shank of the fasteners with a suitable tool. While thepreload is being applied to the bolt having a shank of a fastener, acollar is swaged to the bolt, thereby allowing the fastener (e.g., boltand collar) to retain the cage cover and base together via the force ofthe preload. When the known roller bearing is fully assembled, thefasteners permit the bearing to transmit loads and to maintain a fixedspatial relationship between the cage, races and rollers in theoperational environment of a locomotive.

Such operational environment can be demanding on the ability of thebearing to carry a load for a suitable service life. Generally, theknown bearing is configured to withstand an operating environment wherea shock loading is on the order of 10-15 Gs (i.e., 1 G being anacceleration constant), cage accelerations up to 2000 rpm/sec andbearing resonant frequencies above 70 H and is predicted to have anuseful service life of as long as a million miles. That samebearing—operating under adverse operating conditions—may not fulfill thepredicted service life of a million miles and could be of much lowerduration. For example, the known bearing under adverse operatingconditions, such as, repeated shock loads of approximately 80 Gs, mayhave a useful service life of 300,000 miles or less.

It is believed that bearing performance degradation under the increasedshock loading may be evident in the proximity of the cage fastener. Moreparticularly, the fastener apertures in the open cage may becomeenlarged thereby causing misalignment of the bearing components and, inparticular, separation of the components of the cage. It has been foundthat the known bearing arrangement may experience failure, which isbelieved to be the result of the change in the spatial relationshipbetween cage geometry and fastener geometry while operating underextreme or adverse conditions. In particular, the known bearing has anominal diameter about the central axis of the bearing to the rotationalaxis of the cylindrical roller bearing (the pitch circle diameter) ofapproximately ten inches (10 in.). The known bearing has a two-piececage with a fastener that includes a bolt and a collar. The bolt has ashank with a nominal shank diameter of 3/16 inches, a final length(measured from the inside of the bolt head to the outside of the collar)of approximately 3.4 inches with a surface arranged to engage a portionof the cage. The surface of the shank has a diameter of approximately0.329 inches. The collar has a diameter of approximately 0.300 inchesand includes a surface that engages another portion of the cage. Each ofthe surfaces that engages the respective portion of the cage provides aneffective area in which the head or collar applies a retention force tothe cage. The effective area of the known fastener may be calculated byevaluating the total surface area of the fastener that engages the cage.For example, the respective surface of the bolt head and collar thatengages the cage less the surface area of the aperture in which a shankof the fastener is disposed therein. The effective areas of the knownbolt head and collar are therefore approximately 0.048 in.² and 0.042in.², respectively. Under adverse operating conditions, the knownfastener with these effective areas has been found to be unable toretain the cage for a suitable service life.

J It is recognized engineering practice that, in order to providesufficient clamping force to components in which the fastener is unableto secure the components together, a possible solution is to increasethe size of the bolt head or the collar. Such solution, however, may notbe suitable depending on the operational or physical constraintsspecific to the fastener or the application in which the fastener isbeing used therein. Thus, the application of this engineering practiceis specific to the particular fastening arrangement and the inclinationto apply this solution may not be applicable to fasteners in rollerbearing cage—where the fasteners have been inadequate in retaining thecage under adverse operating condition—once all the components,including the fasteners, of the roller bearing have been evaluated.

In the case of the known bearings, individuals specializing in thefastener art have recommended, upon evaluation of the performance of thefastening arrangement in the known roller bearing in which the fastenershave been inadequate in retaining the cage under adverse operatingconditions, that an increased preload to the fasteners would be requiredto secure the components of the cage together. To ensure that thefastener is able to withstand the recommended increase in preload, theseindividuals have indicated that the nominal size of the shank of thefastener would have to be increased, nominally, from 3/16 to ¼ inches.These individuals have also indicated that an increase in the effectivesurface areas of the fastener would be required to reduce stressconcentration on the cage surfaces. The recommended increase in thepreload would also necessitate a larger bolt head than those of theknown fasteners. Consequently, the fastener apertures in the cage wouldalso have to be enlarged to accommodate the larger shank of such a bolt(i.e., ¼ inch nominal diameter shank) and the known cage configurationmay have to be altered, modified or redesigned to allow a collar to beswaged to the shank. These changes to the cage could affect theperformance of the cage, which may require a roller bearingincorporating these changes in the cage to undergo testing andre-certification before being placed into operational service.

Therefore, it would be desirable to provide for a solution to theproblem of cage separation while utilizing the existing cage and rollerarrangement.

SUMMARY OF THE INVENTION

A preferred embodiment provides for a roller bearing, which may be usedin locomotives that employ a plurality of rollers held between races andsecured by a fastener in a multi-piece cage. In particular, a preferredembodiment provides for a roller bearing. The roller bearing has aninner race, outer race, a plurality of rollers, a roller cage and atleast one cage fastener. The inner race is disposed about a rotationalaxis and includes a peripheral surface facing the rotational axis withan inner nominal diameter of seven (7) inches about the rotational axis.The outer race has a circumferential surface surrounding the inner raceand includes an outer nominal diameter of twelve (12) inches about therotational axis. The plurality of rollers is disposed between the innerand outer races. The roller cage is disposed between the inner race andthe outer race to support the rollers and includes a first piece and asecond piece connected together by the at least one cage fastener. Theat least one cage fastener includes a first surface having a firsteffective area in contiguous engagement with the first piece of theroller cage; and a second surface having a second effective area incontiguous engagement with the second piece of the roller cage. Thefirst and second areas are generally equal to each other.

In another preferred embodiment, a roller bearing is provided. Theroller bearing has an inner race, outer race, a plurality of rollers, aroller cage and at least one cage fastener. The inner race is disposedabout a rotational axis and includes a peripheral surface facing therotational axis with an inner nominal diameter of seven (7) inches aboutthe rotational axis. The outer race has a circumferential surfacesurrounding the inner race and includes an outer nominal diameter oftwelve (12) inches about the rotational axis. The plurality of rollersis disposed between the inner and outer races. The roller cage isdisposed between the inner race and the outer race to support therollers and includes a first piece and a second piece connected togetherby the at least one cage fastener. The at least one cage fastenerextends along a longitudinal axis generally parallel to the rotationalaxis. The at least one cage fastener has first and second surfaces and ashank. The first surface has first effective area in contiguousengagement with the first piece of the roller cage. The second surfacehas a second effective area in contiguous engagement with the secondpiece of the roller cage. At least one of the first and second surfaceshas a diameter about the longitudinal axis greater than 0.375 inches.The shank connects the first and second surfaces and includes a nominaldiameter less than ¼ inches and a length greater than 3.4 inches alongthe longitudinal axis.

In yet another preferred embodiment, a roller bearing is provided with afastener. The fastener secures at least two members of the rollerbearing contiguously together. The at least two members extend along alongitudinal axis over a length of at least 3 inches. The fastenerincludes a shank and a collar. The shank extends between a first end anda second end along a longitudinal axis. The shank has a diameter lessthan ¼ inches to define a shank surface area generally orthogonal to thelongitudinal axis. A shoulder disposed proximate to the first end of theshank. The shoulder has a first clamping area generally orthogonal tothe longitudinal axis. The first clamping area is generally thedifference between a surface area of the shoulder orthogonal to andabout the longitudinal axis and the shank surface area. The collar isdisposed on the shank so that the second end is disposed proximate afrangible portion of the shank. The collar has a bore extending alongthe longitudinal axis between a first collar end and a second collarend. The bore has an internal diameter of less than ¼ inches to receivethe shank. One of the first and second collar ends has a second clampingarea. The second clamping area is generally the difference between asurface area of the first end orthogonal to and about the longitudinalaxis and the surface area of the bore orthogonal to and about thelongitudinal axis. The second clamping area is generally equal to thefirst clamping area.

In a further preferred embodiment, a method of determining a preloadloss capability in a roller bearing having a two-piece cage is provided.The roller bearing has an inner race with an inner nominal diameter ofseven (7) inches and an outer race with an outer nominal diameter oftwelve (12) inches. The two-piece cage has a first piece and a secondpiece with a roller cage disposed between the inner race and the outerrace. A plurality of rollers is disposed between the inner and outerraces and supported by the cage. The first and second pieces areconnected together by at least one cage fastener. The at least one cagefastener includes a first surface having a first effective area incontiguous engagement with the first piece of the roller cage and asecond surface having a second effective area in contiguous engagementwith the second piece of the roller cage. The first and second areas aregenerally equal to each other. The method can be achieved, at least, by:exposing the fastener and the two-piece cage at a temperature ofapproximately 250 degrees Celsius; and determining whether the averageloss of the predetermined preload on the at least one fastener is lessthan 50%.

In another preferred embodiment, a method of preventing separation of atwo-piece cage roller bearing in a two-piece cage is provided. Theroller bearing has an inner race with an inner nominal diameter of seven(7) inches and an outer race with an outer nominal diameter of twelve(12) inches. The two-piece cage has a first piece and a second piecewith a roller cage disposed between the inner race and the outer race. Aplurality of rollers is disposed between the inner and outer races andsupported by the cage. The first and second pieces are connectedtogether by at least one cage fastener. The at least one cage fastenerincludes a first surface in contiguous engagement with the first pieceof the roller cage and a second surface in contiguous engagement withthe second piece of the roller cage. Each of the surfaces engages therespective piece of the cage and provides a respective effective area inwhich the first and second surfaces provide a retention force to thecage. The effective area of the first surface or the second surface isgenerally determined by the difference in the surface area that engagesthe cage at the respective portion less the surface area of an apertureof the cage in which the fastener is supported therein. The method canbe achieved, at least, by: loading the fastener with a predeterminedpreload, the fastener having a shank less than ¼ inches in nominaldiameter; and distributing the predetermined preload equally over thefirst and second effective areas.

BRIEF DESCRIPTIONS OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitutepart of this specification, illustrate the preferred embodiments of theinvention, and, together with the general description given above andthe detailed description given below, serve to explain the features ofthe invention.

FIG. 1A illustrates a first preferred embodiment of a portion of aroller bearing in a sectioned perspective view showing a-two-piece cagewith rollers and a first embodiment of fasteners.

FIG. 1B illustrates a second preferred embodiment of a portion of aroller bearing in a sectioned perspective view showing a two-piece cagewith rollers and a second embodiment of the fasteners.

FIG. 1C illustrates a cross-sectional view of the roller bearingillustrated in FIG. 1A.

FIG. 2 illustrates a plan view of a first part of the first preferredembodiment of the fastener in FIGS. 1A and 1C.

FIG. 3 illustrates a plan view of a second part of the first preferredembodiment of the fastener in FIGS. 1A and 1C.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-3 illustrate the preferred embodiments. In FIG. 1A, there isshown in a perspective view of a first preferred embodiment ofcylindrical roller bearing 10 with varying degrees of sectioning. Thebearing 10 has a cage 40, inner race 12, outer race 14, a plurality offasteners 20 ₁, 20 ₂, 20 ₃, . . . 20 _(N), each of the fasteners 20 ₁,20 ₂, 20 ₃, . . . 20 _(N) can include a bolt 21 with a collar 24, and aplurality of cylindrical rollers 11.

Cylindrical rollers 11 can be made of a suitable material such as, forexample, low carbon, stainless steel or other alloys. Preferably, therollers are formed from AISI 52100 steel for operation at approximately200° C. (390° F.). The rollers 11 are preferably evenly distributedwithin bearing 10 about rotational axis 15. Each of the plurality ofcylindrical rollers 11 preferably has an axis of rotation 16 that isparallel to rotational axis 15. Rollers 11 are free to spin about axisof rotation 16 while being constrained by inner race 12, outer race 14,and cage 40.

When fully assembled, bearing 10 has a toroidal shape with nominalwidth, w, defined between distal end 17 and proximal end 18. Referringto FIG. 1C, bearing 10 is disposed about rotational axis 15 and isradially defined by outer race 14 having an outer face a nominaldistance d from axis 15, and by inner race 12 having inner ring 13 adistance d₁₂ from axis 15. Inner race 12 is radially disposed aboutrotational axis 15 and has a roller face 5, which radially constrainsroller 11 from moving toward axis 15. Outer race 14 has an inner face anominal distance d₁₄ from rotational axis 15 that constrains roller 11from moving radially in a direction away from axis 15. The outer-mostradial face of bearing 10 is the outer face of outer race 14. Inner race12 and outer race 14 preferably have a longitudinal width, which alsodefines the nominal width, w, of bearing 10. And as used herein, theterm “nominal” indicates a suitable dimensional tolerance for theindicated value sufficient for the components of the roller bearing toperform their intended functions.

In a preferred embodiment, cage 40 is radially disposed about rotationalaxis 15 and between outer race 14 and inner race 12. Cage 40 ispreferably formed from brass and is a two-piece construction. Moreparticularly, the preferred embodiment of cage 40 has an open-end cage41 and a cage cover 50. When assembled, cage 40 contains rollers 11between open-end cage 41 and cage cover 50. Preferably, rollers 11 areoriented in cage 40 such that axis of rotation 16 of each roller 11 isparallel with rotational axis 15 and rollers 11 are evenly radiallydistributed about rotational axis 15. To contain the rollers 11,open-end cage 15 preferably has a base 46 toroidally disposed aboutrotational axis 15 and a plurality of fingers 45 that longitudinallyextend from base 46 forming roller pockets 43 therewith. Fingers 45 arepreferably evenly distributed about axis 15. Rollers 11, when setbetween fingers 45 and base 46, are substantially free to spin aboutaxis of rotation 16 while being angularly constrained between the racesby fingers 45. When assembled cover 50 and base 46 constrain rollers 11longitudinally with respect to axis 16.

In the preferred assembled cage 40, each finger 45 has an alignment tab44 located on a circumferential perimeter of the finger that engageswith alignment notch 52 of cover 50. As shown in FIG. 1C, each finger 45preferably has fastener aperture 42, which is radially disposed at anominal distance d_(p) from the rotational axis 15. The radial distanced_(p) is preferably substantially equal to the radial distance betweenrotational axis 15 and axis 16 (i.e., the roller pitch circle radius).As used herein, the lower case nomenclature “d” signifies a magnitude ofa radius of a referenced component with respect to the rotational axis15.

When cover 50 engages open end cage 41 such that alignment tab 44 isaligned with alignment notch 52, fastener aperture 42 of finger 45 ispreferably in alignment with fastener aperture 42 of cover 50. Afastener (e.g., bolt 21 in combination with collar 30 or bolt 21 andcollar 30 with at least one washer) is preferably used to secure cover50 to open end cage 41 by, for example, inserting bolt 21 throughfastener aperture 42 and securing it with flanged collar 30.

The cage fastener 20 preferably includes a bolt 21 (FIG. 2) having ahead 22 of diameter D at its distal end, which is fastened to cage 40with flanged collar 30. The bolt 21 extends along a longitudinal axisA-A, which is preferably parallel to the rotational axis 15. In thepreferred embodiment, bolt 21 is installed such that head 22 engages theouter face of base 46 and flanged collar 30 engages the outer face ofcover 50. More particularly, it is preferred that the pressure appliedby flanged collar 30 to cover 50 is substantially equal to the pressureapplied by head 22 to open end cage 41. In the preferred embodiment theparity in pressure is achieved by providing a collar 30 with aneffective area E_(FF)A₁ that is substantially equal to the effectivearea E_(FF)A₂ of head 22. The effective area E_(FF)A₂ of head 22 may bedefined as that portion of head 22 that engages base 46 (the differencebetween the area of head 22 and area of fastener aperture 42 asreferenced orthogonally with respect to the longitudinal axis).Similarly, the effective area E_(FF)A₁ of collar 30 may be defined asthe area of flange 33 (FIG. 3) minus the area of fastener aperture 42.The equality of pressure may also be achieved by providing a washer(FIG. 1B) between a collar 30 and cage 40 having an effective areasubstantially equal to the effective area of head 22. Alternatively, awasher 38 may be provided, between cage 40 and head 22, having adiameter substantially equal to the diameter of the washer betweencollar 30 and cage 40. The collar 30 may be provided with a constantexterior diameter, which is less than the diameter of the washer. Oneadvantage to providing one or both of these washers is believed to be apropensity of the washers to remain flat against cage 40 even as head 22or flange 33 is urged askew during tightening (e.g. swaging).

In another preferred embodiment, the parity in pressure is achieved byproviding a collar 30 with a clamping area that is substantially equalto a clamping area _(of) head 22. The clamping area of head 22 may bedefined as that portion of head 22 that can be used to clamp againstanother surface (the difference between the area of head 22 and area ofthe shank 28 as referenced orthogonally with respect to the longitudinalaxis). Similarly, the clamping area of collar 30 may be defined as thearea of flange 33 (FIG. 3) minus the area of the bore 35. The equalityof pressure may also be achieved by providing a washer (FIG. 1B) betweena collar 30 and cage 40 having a clamping area substantially equal tothe clamping area of head 22.

The preferred bolt 21 has a shank 28 that extends from head 22 adistance, L_(T), and terminates at pintail 24 (the proximal end 31 ofbolt 21). Shank 28 may be further defined as having a securement sectionof length L_(S) extending from the head 22. The securement section oflength L_(S) may be more particularly characterized as having a grip 29,taper 26, and locking grooves 25. Even more particularly, at a distanceL_(G) from head 22, grip 29 may transition through taper 26 to lockinggrooves 25. Shank 28 has a diameter that varies in the preferredembodiment from the head 22 to the pintail 24. Grip 29 has a nominaldiameter D₁ that is preferably larger than the outside diameter oflocking grooves 25. The diameter of the portion of shank 28 that isfurthest from head 22 is preferably marginally smaller than the outsidediameter of locking grooves 25.

In the preferred embodiments, bolt 21 has a frangible portion 27preferably located between locking grooves 25 and pintail 24. During thefastening of bolt 21 and collar 30 (in a process described below), shank28 is severed in proximity to frangible portion 27. Upon securement ofbolt 21 and collar 30, frangible portion 27 is substantially coincidentwith the proximal end 32 of installed collar 30. The final length,L_(F), of bolt 21 may then be approximated as the distance between head22 and proximal end 32 of collar 30.

FIG. 3 illustrates a preferred embodiment of flanged collar 30 having adistal end 31 and a proximal end 32. The flanged collar 30 is preferablymade of unfinished (e.g. not plated) low carbon steel and has a lengthL_(C). Collar 30 preferably has a barrel 34 at proximal end 32 with anoutside diameter, D_(B), and a flange 33 at distal end 31 with adiameter, D_(F), which is preferably larger than barrel diameter D_(B).Proximate the end 32 of collar 30 there is provided a chamfer. Flangedcollar 30 has a fastener aperture 35 with a diameter, A₁, which ispreferably equal to the diameter of fastener aperture 42 in cage 40.Fastener aperture 42 in collar 30 is preferably concentric with flange33. Approximately at the distal end of chamfer, fastener aperture 42transitions from diameter A₁ to smaller diameter A₂.

Installation of bolt 21 and flanged collar 30 can be as follows. Bolt 21is inserted through fastener aperture 42. Flanged collar 30 is placedover pintail 24. A suitable installation tool is placed over pintail 24to engage proximal end 32 of flanged collar 30. Another suitable toolcan be used to grip pintail grooves 28. The installation tool can bringhead 22 into engagement with open-end cage 41 and to bring flangedcollar 30 into engagement with cover 50 thereby eliminating the gapbetween open-end cage 41 and cage cover 50. As the installation tool isoperated, a swage die moves toward cage 40, swaging the flanged collar50 into the locking grooves 25 of bolt 21, thus providing a permanentlock between bolt 21 and collar 30. After the swaging is completed, thebolt 21 can be separated from the pintail proximate the frangibleportion 27 with a suitable tool.

There are a number of design parameters characterizing bearing 10 thatwere not believed to be important to the performance of the knownbearings for adverse operating conditions prior to applicant'sdevelopment of the preferred embodiments. In particular, therelationships between certain parameter values are believed to improvethe performance of known bearings under conditions of unexpectedvibration and shock, which are summarized in Tables 1 and 2. In thefollowing description, any reference to the dimensions should beunderstood to be the dimensions of the preferred embodiments andvariations due to acceptable tolerances of these dimensions sufficientfor the components of the roller bearing to perform their intendedfunction. TABLE 1 Bolt Dimension Bolt (inches) D - head diameter 0.445D_(l) - grip dia. 0.189 L_(s) - securement length 3.5 L_(f) - finallength 3.6

TABLE 2 Collar Dimension Collar (inches) D_(f) - flange diameter 0.446D_(b) - barrel diameter 0.299 L_(c) - collar length 0.290 A_(l) - collaropening diameter 0.191

Preferred roller bearing 10 has sixteen (16) cylindrical rollers with anominal diameter of 1.5 inches and a longitudinal length 2.441 inches.Outer race 14 has an outer face that is preferably a distance of d asmeasured from rotational axis 15. As used herein, the lower casenomenclature “d” signifies a magnitude of a radius of a referencedcomponent with respect to the rotational axis 15. The outer face of theouter race 14 therefore has a diameter of two (2) times the distance dof the outer race for an outer face diameter of nominally 12.7 inches(320 millimeters). The outer race has an inner face located at adistance d₁₄ from the rotational axis 15. The inner face of the outerrace 14 therefore has a diameter of two (2) times d₁₄ for an inner facediameter of nominally 11.5 inches. The inner ring 13 has a nominaldiameter of two (2) times a distance d₁₂ for a diameter of nominally 7.1inches (180 mm). Thus, the ratio of nominal inner ring diameter(2*d₁₂)—approximately 7.1 inches—to nominal shank or grip diameter(D₁)—nominally 3/16 inches—is approximately 37.3, and the ratio of thenominal diameter at the outer face of outer race nominal diameter(2*d)—approximately 12.5 inches—to nominal shank or grip diameter (D₁)is approximately 66.7. The inner and outer races have a nominal width,w, of approximately 3.4 inches, which is the longitudinal width of theouter race 14 and inner race 12. Cage 40 has a width of approximately3.1 inches. Fastener apertures 42 are located a distance d_(p) from axis15. Similarly, open-end cage 41 (FIG. 1C) has a preferred nominal rollerpitch circle diameter twice that of the distance d_(p) (2*d_(p)) for anominal pitch diameter of approximately 10 inches.

There are preferably sixteen (16) bolts 21 (FIG. 2) inserted in fastenerapertures 42 disposed generally equiangularly about rotational axis 15.Referring to FIG. 2, the preferred embodiment of bolt 21 has a nominalshank or grip D₁ diameter of 3/16 inches and a final length L_(F) ofapproximately 3.5 inches. In a preferred embodiment, bolt 21 also has ahead 22 diameter, D, of 0.445 inches, which is nearly 43% greater thanthe bolt head used in the known bearing cage. The transition betweenhead 22 and grip diameter D₁ of the grip length 29 may have a suitableradius R. The grip diameter D₁ may be slightly larger for a suitabledistance as measured from the tangency of the radius R. Additionally,the shank diameter immediately before the end of grip length 29 may beslightly smaller for a suitable distance.

One can calculate the effective area of head 22 to be the total area ofhead 22 minus the area of fastener aperture 42. One can further definethe head aspect ratio of bolt 21 to be the ratio of final length, D_(F)to head diameter, D. The preferred bolt will therefore have an aspectratio of ten (10), and a total effective area of 0.127 in.² per bolt;reflecting an approximately 29% decrease to the aspect ratio over thebolts in the known bearing and increase in effective area of over 160%.Bolt 21 preferably has locking grooves 25 with an approximate outerdiameter of between 0.185 and 0.177 inches. There may further be a taper26 between grip 29 and locking grooves 25 and there may also be a tapersubstantially at the transition from the locking grooves 25 to taper 26.There may further be a radiused portion where taper 26 meets lockinggroove 25. At the end of securement length L_(S) opposite head 22, thereis a transition to break-off point 27. In the preferred embodiment head22 has a diameter, D, that is nominally between 2.2 and 2.5 times thediameter of grip 29.

The preferred embodiment of flanged collar 30 has flange diameter, D_(F)of 0.446 inches, and a barrel diameter, D_(B), of 0.299 inches. Thefastener aperture 42 in flanged collar 30 has a diameter, A₁, of 0.191inches, which is less than 0.25 inches or nominally ¼ inches. Thepreferred effective area of flange 33 is therefore 0.128 in.² and issubstantially equal to the effective area of head 22. This represents anincrease of over 200% in comparison to the effective area of the knownflange.

Both the bolt head and the collar flange are believed to minimizeloading on the bolt, and it is therefore significant that the effectivecontact area per head/flange combination (the total contact area) isapproximately 0.26 in.² in the preferred embodiment; representing anincrease of greater than 180% over the known fasteners. For all sixteenbolts, there is preferably a total contact area of approximately foursquare inches (4 in.²). Furthermore, as one can define the aspect ratioof bolt 21, so too can one define a head/collar aspect ratio as the sumof the diameters of head 22 and flange 33 (e.g., D+D_(F)=0.9 inches)divided by the final length of bolt 21 (e.g., L_(F)=3.5 inches)resulting in a preferable head/collar aspect ratio of approximately four(4) compared to a head/collar aspect ratio in fasteners of similarlysized known bearings of approximately 5.5. It is also relevant thatfinal length L_(F) of bolt 21 (in inches) is approximately 64% greaterthan the total effective contact area per bolt (i.e. the sum of theeffective areas of the collar flange and the bolt head) in squareinches.

There is also believed to be a significant relationship between thetotal effective contact area and the overall dimensions of the bearing.The nominal pitch diameter of bearing 10, measured about the rotationalaxis 15 to the center point of respective fastener apertures 42, isapproximately ten inches (10 in.) and is approximately 2.5 times thetotal effective contact area (approximately 4 sq. in.) for all sixteen(16) bolts. With a preferred roller length of 2.441 inches and apreferred roller diameter of 1.496 inches, the aspect ratio of thepreferred roller is about 1.632 (roller length/roller diameter). Havinga preferred bolt head aspect ratio of ten (10), the preferredcombination of bolt 21 and bearing 10 may be characterized by a boltaspect ratio that is approximately six (6) times the roller aspectratio. In comparison with known bearings, the known bearings have annominal inner race diameter (2*d₁₂) to nominal grip diameter D₁ ratio ofapproximately 37.3, resulting in the ratio of the known head/collaraspect ratio over 55% greater than the pitch pocket diameter.

One may similarly compare the race diameter ratio (the ratio of theouter diameter of outer race 14 to the inner diameter of inner race 12)to the head/collar aspect ratio (the ratio of the sum of the diametersof head 22 and flange 33 to the final length of bolt 21). The preferredbearing has a head-collar aspect ratio of approximately 3.5 times theratio of the outer race to the inner race diameters.

To evaluate whether the preferred fastener for a roller bearingaccording to the preferred embodiments would provide an adequate servicelife compared to the known roller bearings, testing was performed toprovide a basis for comparing the known bearings to the preferredembodiments. Applicant believes that the ability to maintain a setpreload at high temperature is indicative of the ability of the bearingto provide a suitable service life under adverse operating conditions.Hence, the known roller bearing and the roller bearing of the preferredembodiments were subjected to the simulated stress of varying magnitudeof high temperatures in a series of test. In particular, to infer theincreased loading capacity of the preferred embodiment, the averagepre-load loss under thermal stresses for three (3) fastenerconfigurations were determined; two (2) in accordance with the preferredembodiments, and one (1) in accordance with the known fastenerconfiguration. In each configuration, the shank diameter of the boltranged from 0.1880 inches to 0.1895 inches, or nominally 3/16 inches,which is less than 0.25 inches or nominally ¼ inches. The tested knownbolt (Pin #1) had a head diameter that ranged from 0.297 to 0.327inches, with a grip length of between 3.147 to 3.157 inches. The bolt ofthe preferred embodiment (Pin #2) had a head diameter of between 0.430and 0.460 inches with a grip length of between 3.210 and 3.220 inches.Thus, the average head diameter was approximately 43% greater in thepreferred embodiment while the shank diameter and grip length rangesremained nominally equal.

Two collars were tested. The first (Collar #1), a known collar, had aflange diameter of between 0.297 inches to 0.327 inches with a totalcollar length of between 0.235 and 0.255 inches. The barrel diameter ofthe known collar was nominally equal to the flange length ranging from0.297 to 0.302 inches. The second collar tested (Collar #2), that of thepreferred embodiment, had a flange diameter of 0.440 to 0.450 inches, abarrel diameter of between 0.297 and 0.301 inches, and total length of0.285 to 0.295 inches. In a third configuration, a washer having anoutside diameter of 0.438 inches, an inside diameter of 0.188 inches,and a thickness of 0.063 inches was used.

Tests were performed on three (3) cage assemblies using the three (3)fastener configurations. The first assembly (cage 1) was configured withthe three configurations throughout the sixteen (16) fastener apertures.The distribution of fastener configurations was as follows: 1)Configuration 2 in eight (8) of the sixteen (16) fastener apertures; 2)Configuration 3 in four (4) of the sixteen (16) fastener apertures; and3) Configuration 1 in each of the remaining four (4) fastener apertures.

Configuration 2 was used exclusively in each of the fastener aperturesof the second cage tested (Cage 2). The third cage tested (Cage 3) usedonly Configuration 3 fasteners in the assembly.

During testing, four (4) fasteners of each cage were preloaded at roomtemperature. The average preload is at least 1000 pound-force (lbf.) andpreferably 2200 lbf. Thereafter, each cage was sectioned; one-half (½)of the remaining twelve (12) fastener assemblies in each cage beingheated to 200° C., the other half being heated to 250° C. The residualpre-load torque in each of the remaining six (6) fasteners was measuredby comparing fastener parameters before and after heating, as shown inTable 3 to determine the average preload loss. Table 3 indicates that ata high temperature, such as 250° C., the known bearing lost aproportionally greater amount of preload than the preferred embodiments,as shown by configurations 2 and 3 in Table 3 below. TABLE 3 Comparisonof Preload Loss under Thermal Stress. Average Average Average PreloadPreload Preload Loss @ Loss @ Loss @ Roller Bearing 150° C. 200° C. 250°C. Known Bolt and Collar (Config. 1) 141 lbf. 1208 lbf.  New Bolt andNew Collar (Config. 2) N/A  91 lbf. 512 lbf. New Bolt with Known Collarand N/A 161 lbf. 694 lbf. Washer (Config. 3)

In particular, at a temperature of 200° C., there was found an averagepre-load loss in fastener configuration #2 of 91 lbf, and an averagepre-load loss in fastener configuration #3 of 161 lbf. At 250° C., theaverage pre-load loss for the known fastener (Configuration #1) was 1208lbf for average preload loss of over 50% from the original preload. At250° C., the average preload loss for a preferred embodiment of thefastener (Configuration #2) was 512 lbf for an average preload loss ofabout 23%, whereas the average pre-load loss for another preferredembodiment (Configuration #3) was 694 lbf for an average preload loss ofabout 31% from the original preload. Based on Table 3, it is believedthat the preferred embodiments (Configurations 2 and 3) would be able toprovide for a suitable service under adverse operating conditions.Applicant has determined that a preload loss of less than 50%—sandpreferably 35% or less—under the conditions specified herein isacceptable to demonstrate a suitable service life under adverseoperating conditions.

While the present invention has been disclosed with reference to certainembodiments, numerous modifications, alterations and changes to thedescribed embodiments are possible without departing from the sphere andscope of the present invention, as defined in the appended claims.Accordingly, it is intended that the present invention not be limited tothe described embodiments, but that it has the full scope defined by thelanguage of the following claims, and equivalents thereof.

1-25. (canceled)
 26. A method of determining a preload loss capabilityin a roller bearing having a two-piece cage, the roller bearingincluding an inner race with an inner nominal diameter of seven (7)inches and an outer race with an outer nominal diameter of twelve (12)inches, the two-piece cage having a first piece and a second piece, aroller cage disposed between the inner race and the outer race tosupport a plurality of rollers disposed between the inner and outerraces, the roller cage having a first piece and a second piece connectedtogether by at least one cage fastener, the at least one cage fastenerincluding a first surface having a first effective area in contiguousengagement with the first piece of the roller cage and a second surfacehaving a second effective area in contiguous engagement with the secondpiece of the roller cage by application of a predetermined preload, thefirst and second areas being generally equal to each other, the methodcomprising: exposing the fastener and the two-piece cage at atemperature of at least approximately 250 degrees Celsius; anddetermining whether the average loss of the predetermined preload on theat least one fastener is less than 50%.
 27. The method of claim 26,wherein the determining comprises assessing whether the average loss ofthe predetermined preload is less than 35%.
 28. The method of claim 26,wherein the exposing comprises preloading the fastener with at least1000 pound of force at a temperature below 150 degrees Celsius.
 29. Themethod of claim 28, wherein the applying further comprises swaging thefastener proximate one of the first and second pieces.
 30. A method ofpreventing separation of a two-piece cage roller bearing in a two-piececage having an inner race with a nominal inner diameter of seven (7)inches and an outer race with an outer nominal diameter of twelve (12)inches, the two-piece cage having a first piece and a second piece, aroller cage disposed between the inner race and the outer race tosupport a plurality of rollers disposed between the inner and outerraces, the roller cage having a first piece and a second piece connectedtogether by at least one cage fastener, the at least one cage fastenerincluding a first surface in contiguous engagement with the first pieceof the roller cage and a second surface in contiguous engagement withthe second piece of the roller cage, each of the surfaces that engagesthe respective piece of the cage provides a respective effective area inwhich the first and second surfaces provide a retention force to thecage, the effective area of the first surface or the second surfacebeing determined by the difference in the surface area that engages thecage at the respective portion less the surface area of an aperture ofthe cage in which the fastener is supported therein, the methodcomprising: loading the fastener with a predetermined preload, thefastener having a shank less than ¼ inches in nominal diameter; anddistributing the predetermined preload equally over the first and secondeffective areas.
 31. The method of claim 30, wherein the loadingcomprises preloading the fastener with at least 1000 pound of force. 32.The method of claim 31, wherein the distributing further comprisesswaging the fastener proximate one of the first and second pieces of thecage.